1. Field of the Invention
This invention relates to the treatment of toxic wastes. The invention is particular by suitable for, but not limited to, the thermal desorption of hydrocarbon contaminants from soils.
The contaminants may include, but are not limited to, petroleum products (e.g. petrol, oils, greases); phenols; coal tars; cyanides; pesticides; PCB's and HCB's .
2. Prior Art
The treatment of contaminated soils is a world-wide problem. Often the soils are simply removed and transferred to a toxic waste dump. This does no more than move the problem.
Where thermal treatment of the wastes is effected, the traditional method is by direct heating in a rotary kiln. Indirect treatment methods include (a) the externally heated rotary kilns (where the heat is transferred through the kiln wall to the soil) and (b) auger-type heaters, where heat is applied to the soil through the heater casing and/or the flyte(s), of the auger e.g. by the circulation of hot oil. With such methods, the soil may only be heated to approximately 150.degree.-450.degree. C. and many contaminants may not be treated at those relatively low temperatures.
For contaminants such as PCB's , the Environmental Protection Authorities around the world specify strict conditions for their disposal in very high temperature incinerators, e.g. found on the vessel "VULCANUS".